1. Field of the Invention
The present invention relates to an air mattress, and in particular to an air mattress which is capable of preventing a side portion of the same from being expanded by an air pressure.
2. Description of the Background Art
Generally, a mattress having a wire spring therein has been largely used as a bed mattress. As the time of use of the above mattress increases, the electric force of the wire spring may decrease, so that a recovering force may be lost. So, it is impossible to maintain an inherent shape of the mattress.
When a user lies on the conventional mattress, an over pressure could be applied to the portions of the mattress contacting with a user's body since the elastic force of the wire spring installed in the interior of the mattress is not uniformly applied to the entire portions of a user's body, namely, only certain portions of the user's body are contacted.
Therefore, it is very hard for the user to maintain a proper posture, and the portions of the user's body contacting with the mattress may have big stresses.
So as to overcome the above problems, an air mattress is developed. However, since the side portions of the conventional air mattress may be abnormally expanded due to the air pressure, it is impossible to stably support the user's body. In addition, the outer look of the conventional air mattress having expanded side portions is poor.